Storage systems generally have one or more storage apparatus. Each of the storage apparatus has an HDD (Hard Disk Drive) or an SSD (Solid State Drive) as a storage device. A storage system is accessible by one or more host apparatus, e.g., a host computer, via a network such as a SAN (Storage Area Network) or a LAN (Local Area Network). Generally, storage apparatus are rendered highly reliable by a reliability enhancing process according to the RAID (Redundant Array of Independent (or Inexpensive) Disks) technology.
Patent Document 1 discloses an information system that is capable of improving availability. According to Patent Document 1, a first volume of a first storage apparatus and a second volume of a second storage apparatus are provided as identical volumes to a host computer. The host computer recognizes the first volume and the second volume as identical volumes with different buses.
Patent Document 2 discloses an HA (High Availability) pair configuration in which a first volume of a first storage apparatus and a second volume of a second storage apparatus respond to a host computer with identical virtual IDs. According to Patent Document 2, when the first storage apparatus and the second storage apparatus receive an offloaded data copy command indicating the virtual ID as a copy destination from the host computer, the first storage apparatus and the second storage apparatus select either the first volume or the second volume as a copy source volume depending on the storage apparatus where the copy destination volume exists, and copy data from the selected copy source volume to the copy destination volume.